Pull down mechanism for projection machine



w. WELLS PULL bowu MECHANISM FOR PROJECTION MACHINE Filed April 12, 1967 Aug. 12, 1969 2 Sheets-Sheet -1 JNVENTOR.

Leo/v W Wsus %d7(/} 4 meme-ks Filed April 12] 1967 PULL DOWN MECHANISM FOR PROJECTION MACHINE INVENTOR.

HTTOPNEYS 2. Sheets-Sheet a Lea/v W wms United States Patent 3,460,888 PULL DOWN MECHANISM FOR PROJECTION MACHINE Leon W. Wells, Closter, N.J., assignor to Panopix Research Inc., New York, N."Y., a corporation of New York 1 Filed Apr. 12, 1967, Ser. No. 630,343

Int. Cl. G03b 41/00 I US. Cl. 35283 1 6 Claims ABSTRACT OF THE DISCLOSURE Cross reference to related application The present application describes an improvement in certain features of the apparatus shown and described in my prior application entitled Improved Motion Pitcure Projector, Ser. No. 541,196, filed Apr. 8, 1966.

Background of the invention In the prior application identified above, a vertically movable platform carries filnr and film moving mechanisms for projecting sequential rows of picture frames from motion picture film, the platform being stepped vertically upwardly between successive rows whereby to align the rows with a projection system. At the conclusion of the projection cycle, that is, after the last row of picture frames has been projected and the film withdrawn into a removable cartridge, terminal cycling means are energized which connects a drum to a power system whereupon the drum is rotated and a cable drawn in thereby, the cable is trained over suitable pulleys on the frame'and platform and effects a pull-down of the platform. That is, the platform is then pulled down to a starting" position for commencement of a new cycle of operation. As shown in that application, 'coil springs are employed for urging the platform upwardly and an escapement mechanism is actuated at the end of each row of picture frames, except the last, to permit the platform to move upwardly one :stepvThe present invention also constitutes an improvement in the springerrangement for urging the platform upwardly.

Summary'of the invention- Whereas my prior application employed a single cable for pulling the platform downwardly, the present invention involves the use of two cables so wound on a winch drum that they are simultaneously pulled downwardly equal amounts and are attached to separated means on the platform so as to ensure pulling all parts of the platform downwardly by the same amount, thus relieving guide means of binding and preventing unwanted tilting of the platform. The other ends of the cables are also attached to the paltform but extend downwardly thereto so as to further ensure uniform vertical movement of all of the spaced portions of the platform. Negator spring means are employed to urge the platform upwardly in lieu of the coil springs described in my prior application.

Brief description of the drawings FIG. 1 is a highly schematic illustration of a portion of a projection machine diagrammaically illustrating only those portions thereof relating to the present invention;

FIG. 2 is a horizontal sectional view taken substantially along the line 2-2 of FIG. 1; and

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FIG. 3 is a fragmentary side view of the drum and clutch portion of FIG. 1.

Description of the preferred embodiment In the drawings, numeral 2 indicates a vertically movable platform having means thereon for advancing a film 4 along a predetermined path through a projection zone (not shown) whereby successive horizontal rows of picture frames 6 are sequentially projected, the direction of film travel being reversed at the end of each row. The topmost row of picture frames is projected first and at the end thereof a signal causes actuation of an escapement mechanism, fully described in my prior application, to permit the platform 2 to move upwardly one step under the influence of spring means and the direction of film travel is reversed and the next row of frames in projected. At the completion of projection of the last or lowermost row of picture frames, the film continues to move into a cartridge and when the end thereof reaches a position adjacent the cartridge, signal means thereon actuate a switch to initiate a terminal cycle of operation. That terminal cycle includes completion of a circuit through a solenoid to effect connection of a winch drum to the power source to thereby pull the platform downwardly to its starting position.

In the drawings, platform 2 is schematically shown as provided with depending legs 8 guided by'suitable guide means (not shown) for vertical movement. Secured to each leg 8, near the bottom thereof, is an end of a negator spring 12. As known to those in the art a negator spring is normally curled to a spiral configuration, each increment being bent to the same radius of curvature. Straightening such spring to a straight condition and permitting it to then rewind on itself will result in the exertion of a constant force, irrespective of the extent to which the spring is extended. As shown, each negator spring extends upwardly along its associated leg 8 and then outwardly over a suitable roller 14 journalled on support means 16 fixed to the base 18 of the machine. It will be apparent to those skilled in the art that the springs 12 constantly tend to roll themselves up about the' rollers 14 and thus exert a constant upward force on the legs 8, that force being constant irrespective of the vertical position of the platform 2. 1

Also mounted on suitable fixed support means, for example, the upstanding brackets 10, .are. three pairs of guide pulleys 20, 22 and,24. Securing means 26 are fixed to the legs.8 and move"v therewith. A winch drum 28 is, journalled on an upstanding. shaft 30, the upper end of which is journalled in a bracket 32 fixed tothe projector base, 18. The winch drum 28 is rotatable on the shaft 30 and is provided at its upper end with clutch teeth 34. A clutch element 36' is also journalled on the shaft 30 and includes a gear 38 rigid therewith and which gear is connected to a suitable gear train extending from a power source, not shown. The clutch member 36 and its gear 38 are vertically slidable on the shaft 30 and vertical movement thereon is controlled by a solenoid 40, see FIG. 3, acting through a lever 42 pivoted to the machine frame at 44. A spring 46 normally biases the lever 42 to lift the clutch element 36 upwardly and thereby disengage the same from clutch teeth 34 whereupon the winch drum 28 is free to rotate on shaft 30 in either direction. The solenoid 40 is energized by the signal means previously referred to as initiating the terminal cycle of the machi e. A pair of flexible filaments, such as the cables 48 and 50, are separately Wound on the Winch drum 28. As shown, the midportion of each cable is wound about the drum for a turn or two and both ends extend therefrom. One end of the cable 50 extends around a guide pulley 24, then upwardly where it is secured to the securing means 26 on the adjacent leg 8. A corresponding end of the cable 48 is likewise trained about the other guide pulley 24 and secured to the securing means 26 on the other leg. The other end of each cable is trained about its corresponding guide pulley 22, then upwardly over its upper guide pulley 20, then downwardly where it too is secured to the securing means 26. The arrangement is such that both cables 48 and 50 are wound about the drum 28 in the same direction and the guide pulley and cable length are so positioned and dimensioned that both cables are taut at all times.

As will be obvious, rotation of the drum 28 in a clockwise direction, as viewed from the top thereof, will permit the portions of the cables trained over pulleys 24 to pay out and thus permit upward movement of the platform 2. Such clockwise rotation, however, is only possible when the clutch member 36 is disengaged from the drum and this is the condition that exists during a projection cycle. It will also be apparent that such clockwise rotation of the drum also pulls in on those portions of the cables guided by pulleys 22 and 20 whereupon the securing means 26 are constrained to move upwardly equal amounts, corresponding to the amount of cable that is unwound from the drum. Thus, the cables constitute control means whereby the platform 2 may move upwardly freely under the influence of the springs 12 but wherein both securing means 26 are constrained to move equal amounts, thus relieving the guide means for legs 8 of strains occassioned by any rocking or tilting of the platform 2. It will also be obvious that, upon energization of the solenoid 40 during a terminal cycle of the machine, the clutch member 36 will be engaged with the Winch drum 28 and will positively drive the same in a counterclockwise direction, as seen looking downwardly on FIG. 1. This rotation will forcibly reel in those portions of the cable trained around pulleys 24 and thus forcibly pull the platform downwardly while the other end portions of each cable will pay out at the same rate and thus prevent either of the securing means 26 from overrunning the other securing means.

Preferably intermediate portions of the cables wound on the drum 28 are secured thereto to ensure against any slippage, for example, the drum may be provided with openings therethrough through which a portion of the cables extend to ensure against slippage.

While a single specific embodiment of the invention has been shown and described herein, it is to be understood that other modifications may be restored to within the scope of the appended claims.

What is claimed is:

1. In a motion picture projector having a vertically movable platfrom carrying film advancing means thereon, which platform moves upwardly during a projection cycle, and having terminal cycling means responsive to completion of a projection cycle for initiating return of said platform to a lower position, the improvement comprising: a winch drum; at least two cables, each having a first portion wound about said drum with one end portion extending from said drum, the said one end portions of said cables being secured to said platform at laterally spaced securing means; cable guide means guiding said end portions upwardly to said spaced securing means, said first portions being wound on said drum in the same direction whereby rotation of said drum in one direction pulls said spaced means downwardly equal amounts without tilting said platform; and energizing means responsive to said terminal cycling means for rotating said drum in said one direction.

2. A projection machine as defined in claim 1 wherein said platform comprises laterally spaced depending legs and platform guide means guiding said legs for vertical movement; said spaced securing means being, respectively, closely adjacent said legs.

3. A projection machine as defined in claim 1 wherein said first portion of each cable is an intermediate portion thereof, the other end portion of each cable being secured to said platform at laterally spaced positions there on; said cable guide means including means guiding said other end portions downwardly to said laterally spaced positions, said guide means holding all said cable portions taut whereby said cables prevent tilting of said platform during both upward and downward movement thereof.

4. A projection machine as defined in claim 1 wherein said energizing means includes a clutch for drivingly connecting said drum to a source of power; and a solenoid for actuating said clutch.

5. In a motion picture projector having a vertically movable platform carrying film advancing means thereon, which platform moves upwardly during a projection cycle, and having terminal cycling means responsive to completion of a projection cycle for initiating return of said platform to a lower position, the improvement comprising: negator spring means arranged to constantly urge said platform upwardly with constant force; and means responsive to said terminal cycling means for moving said platform downwardly against the action of said negator spring means.

6. A projection machine as defined in claim 5 wherein said platform comprises laterally spaced depending legs and platform guide means guiding said legs for vertical movement; there being one of said negator springs adjacent each of said legs.

References Cited UNITED STATES PATENTS JULIA E. COINER, Primary Examiner U.S. Cl. X.R. 352-8, 123 

